In vivo measurements of limbic glutamate and GABA concentrations in epileptic patients during affective and cognitive tasks: A microdialysis study

Modulation of intracortical circuits in primary motor cortex during automatic action tendencies

Humans display automatic action tendencies toward emotional stimuli, showing faster automatic behavior (i.e., approaching a positive stimulus and avoiding a negative stimulus) than regulated behavior (i.e., avoiding a positive stimulus and approaching a negative stimulus). Previous studies have shown that the primary motor cortex is involved in the processing of automatic actions, with higher motor evoked potential amplitudes during automatic behavior elicited by single-pulse transcranial magnetic stimulation. However, it is unknown how intracortical circuits are involved with automatic action tendencies. Here, we measured short-interval intracortical inhibition and intracortical facilitation within the primary motor cortex by using paired-pulse transcranial magnetic stimulation protocols during a manikin task, which has been widely used to explore approaching and avoiding behavior. Results showed that intracortical facilitation was stronger during automatic behavior than during regulated behavior. Moreover, there was a significant negative correlation between reaction times and intracortical facilitation effect during automatic behavior: individuals with short reaction times had stronger faciliatory activity, as shown by higher intracortical facilitation. By contrast, no significant difference was found for short-interval intracortical inhibition between automatic behavior and regulated behavior. The results indicated that the intracortical facilitation circuit, mediated by excitatory glutamatergic neurons, in the primary motor cortex, plays an important role in mediating automatic action tendencies. This finding further supports the link between emotional perception and the action system.

The role of glutamate and GABA in cognitive dysfunction in schizophrenia and mood disorders - A systematic review of magnetic resonance spectroscopy studies

Epidemiologic, genetic, and neurobiological studies suggest considerable overlap between schizophrenia and mood disorders. Importantly, both disorders are associated with a broad range of cognitive deficits as well as altered glutamatergic and GABAergic neurometabolism. We conducted a systematic review of magnetic resonance spectroscopy (MRS) studies investigating the relationship between glutamatergic and GABAergic neurometabolites and cognition in schizophrenia spectrum disorders and mood disorders. A literature search in Pubmed of studies published before April 15, 2019 was conducted and 37 studies were deemed eligible for systematic review. We found that alterations in glutamatergic and GABAergic neurotransmission have been identified relatively consistently in both schizophrenia and mood disorders. However, because of the vast heterogeneity of published studies in terms of illness stage, medication exposure, MRS acquisition parameters and data post-processing strategies, we still do not understand the relationship between those neurotransmitters and cognitive dysfunction in mental illness, which is a critical initial step for rational drug development. Our findings emphasize the need for coordinated multi-center studies that characterize cognitive function and its biological substrates in large and well-defined clinical populations, using harmonized imaging sequences and analytical methods with the goal to elucidate the underlying pathophysiological mechanisms and to inform future clinical trials.

The chronic exposure to abamectin causes spatial memory deficit and depressive behavior in mice

It is known that abamectin (ABA), which is a component belonging to the group of avermectins, has been broadly used as biopesticide. Although its effect on non-target aquatic organisms is known, knowledge about its impacts on terrestrial animals such as mammals remains incipient. Thus, we aim at investigating the effects (phycical and neural-behavioral) from the chronic exposure (90 days) to ABA (1/10 of LD₅₀) on Swiss and C57Bl/6J mice from both sexes. Accordingly, at the end of the experimental period the animals were subjected to the following tests: Novel Object Recognition Test (NORT), Morris Water Maze (MWM), Tail Suspension Test (TST), and Forced Swimming Test (FST). We showed that the new-object recognition indexes in the NORT test sessions did not differ between experimental groups; however, animals exposed to ABA, regardless of sex or strain, recorded longer latency time to find the quadrant holding the platform in the MWM training sessions, as well as stayed shorter in this quadrant. Such results highlight the negative effect of the pesticide on the animals' spatial memory evocation, without evident influence from their genetic status and sex. With regard to TST, we also did not observe differences in immobility time between groups; however, Swiss mice (males and females) presented depressive behavior in the FST, and apparent influence from their genetic status in their responses during the test. Therefore, our study confirms the neurotoxic potential of ABA and is pioneer in reporting memory deficit and depressive behavior in mammal experimental models.